In a conventional dragline machine the hoist line is wound on one drum and the dragline is wound on a separate drum. After the bucket is dropped and the dragline reeved in to fill the bucket, tension must be maintained on the dragline during hoisting to prevent the bucket from dumping until the desired location is reached.
In U.S. Pat. No. 4,143,856, there is disclosed a split drive from an engine to separate torque converters selectively clutched to the respective hoist and dragline drums with a selectively engageable power interlock for coupling the output of both torque converters together in parallel to jointly power either of the drums as desired. In that system, either of the hoist or dragline controls, when moved in one direction, is operative to modulate both torque converters when the power interlock is engaged.